Combustion engine



Dec. 24, 1935. w. HARPER, JR

COMBUSTION ENGINE Filed March 27, 1933 2 Sheets-Sheet l CONNECTED TO SOURCE OF' TIMED INTERRUPTED CURRENT INVENTOR WILLIAM HARPER, JR.

ATTORNEY Dec. 24, 1935.

ELECTRICAL IGNITION EFFICIENCY-PERCENT w. HARPER, JR 2,025,203

COMBUSTION ENGINE Filed March 27, 1953 2 Sheets-Sheet 2 PRIMING PLUG 150 500 2ooo TEMPERATURE DEGREES E CONNECTED TO SOURCE OF TIMED INTERRUPTED CURRENT CONNECTED TO SOURCE OF TIMED INTERRUPTED CURRENT INVENTQR WILLIAM ATTORNEY HARPER, JR.

l I Patented Dec. 24, 1935 UNlTED s'rArss PATENT OFFICE COMBUSTION ENGINE William Harper, In, Port Washington, N. Y., assignor to H. B. Motor Corporation, a corporation of New York Application March 2'1, 1933, Serial No. 662,893

23 Claims.

This invention relates to combustion engines and is 'a continuation in part of my applications Serial No. 509,947, filed January 20, 1931, and Serial No. 646,224, filed December 8, 1932.

The object of this invention is to provide an improved ignition system and method whereby to increase the power output and general overall eflicieney of combustion engines, and particularly high speed, high compression engines wherein such high temperatures are developed as to produce troubles both from fouling of the spark plugs and impairment of the designed spark plug insulation.

Ordinary spark plugs retain their designed insulation and capacity for conducting away the heat without fusing the porcelain or other insulation up to and beyond moderate high speeds. When very high speeds are used, as is the tendency in modern combustion engine development, the period between explosionsis so short that ordinary plugs readily become overheated, and thereby tend to lose their insulation and may even fuse, as well as crack the fuel and foul by the deposited carbon. To meet this condition plugs are obtainable on the market which have a good heat conducting capacity, but at the expense of high insulating quality, and also plugs have been developed having a very high insulating quality but at the expense of heat conducting capacity.

A peculiar phenomenon occurs in the normal operation of common insulated spark plugs, to wit: It is an established fact that porcelain, mica and other porous insulating materials have a pronounced catalytic action in the decomposition of hydrocarbons at various temperatures. In the presence of such porous materials radiant heat will break down free carbon first, and combined carbon secondly, into component gases, the ultimate being CO2 and water vapor. The critical temperature at which this phenomenon occurs in the presence of the catalyst is approximately 750 F. Hence if any part of the spark plug attains a temperature of 750 F. the radiant heat thrown off will start this reaction which is accumulative in the temperature range.

It also happens that the above decomposition gases such as carbon dioxide, and to a lesser extent carbon monoxide, are very good conductors of high tension current especially when they are intensified by high compression. Therefore as any point of the spark plug reaches or exceeds the above critical temperature, gases developed in the proximity of the spark gap will progressively bleed the potential of the discharge until the discharge of the hot spark will disappear completely and the plug will be shorted by a gas pocket.

In operating an engine under these conditions the performance is deceptive as to the real cause of incomplete combustion. As the engine begins 5 to miss the indications are that the mixture is too lean as an examination of the spark plugs will show that they are perfectly clean and functioning properly. The natural thing to do is to enrich the mixture which thus prevents the missing 10 and allows the motor to increase its power output. However, if an examination is made of the analysis of exhaust gases from an engine operated under these conditions a large percentage of CO running anywhere from 1% to 7% will be in evil5 -dence in the exhaust. This is unnatural in that as the temperature and speed of an engine are increased the thermal efllciency of the fuel should also increase.

There are thus two conditions under which a 20' spark plug will fail to function as an igniting point for compressed gas. One is when the plug is too cold and causes short-circuiting on the surfaces of its insulation due to the deposit of condensed carbonaceous matter acting as a con- 25 ductor of high tension current. The other condition is the other extreme, at which the plug becomes too hot, although perfectly clean, and spontaneously with its temperature develops an invisible gas conductor which short-circuits the 30 high tension current in the gap of the plug without developing sumcient heat energy to brin about ignition. Difiiculties due to inefilclent spark plug ignition resulting in excessive fuel consumption are 35 quite noticeable in automobiles which follow the modern trend of higher motor speeds and higher compression ratios to obtain higher efllciency. Theoretically, increased motor speeds and compression ratios should result in increased efli- 40 ciency but in practice this is not the case, one particular eight-cylinder car in the low price field using as much fuel as a much larger and heavier automobile. Another somewhat larger car uses dual ignition, or two spark plugs in each cylinder, in order to obtain more rapid flame propagation and partially compensate for the loss of efliciency due to higher compression and temperature at the spark plugs. After considerable study and discussion with various carbureter experts it is for combustion engines which largely overcomes the above diiliculties with little or no change in the ylinder head construction of-cars-and motors now on the market. It employs a plurality of spark plugs in constant or permanent communication with the combustion space, having 1 vidual electrical ignition characteristics which vary'over the range of temperatures developed in the combustion space and a combined electrical ignition characteristic which under all conditions -is at least equal to the maximum ignition emciency of either plug alone.

While the invention is not limited to two spark plugs in each combustion space I havefound two plugs sumcient in all my experiments. One of these plugs is of the high insulation, less heat conducting type or what I call the low temperaveloped in the combustion space when the engine is operated at high speeds.

Under starting conditions and idling and low speeds the priming plug functions in the usual way, having suilicient insulating surface to prevent fouling. As the temperature increases the electrical ignition emciency of this plug will diminish due to the presence ofthe short-circuiting element of gas generated in the zone of the spark .gap, until it may have but 25% or less of its origwhen used alone.

inal potential in the center of. hotness of its spark. While this condition is being approached, the increasing temperature will have cleaned the cold plug of any surface condensation which may have caused leakage and short-circuiting of the high tension current, and when this deposit is burned 011 the cold plug, which is connected in circuit so as to be energized simultaneously with the priming plug, will function as the main ignition point at 100% of its electrical efficiency.

When an engine equipped with my ignition system is run at high speeds the electrical ignition efllciency of the cold plug is 100% and that of the priming plug may be around 25%, making a total electrical ignition efficiency of approximately 125% as compared with the maximum efficiency of the cold plug alone, whereas the combined efllciency of two priming plugs would under the same conditions be but 50%. Of course, it would be desirable to combine the ignition characteristics of two cold plugs but because of the rapid heat dissipating properties of such plugs they would foul and be ineffective under starting conditions or continued idling, and therefore unreliable There are certain situations in which it is desirable, and others in which it is essential, to shield the primingplug to protect it against excessive radiant heat. For example, in a two-cycle engine twice as much heat will be developed in a given time than in an equal time and number of revolutions by a four-cycle engine. In most twocycle engines I therefore prefer to shield the priming plug in a recess having a restricted passage leading into the combustion spaceas disclosed in engine embodying the invention;

;tain higher speeds it becomes increasingly desirable to shield the priming plugagainst the ras diant heat.

There are also situations in which it is desirable or essential to shield the priming plug for reasons other than protection against radiant heat; The chief of these reasons is that the modern trend is 10 to use alcohol and other fuels which are less inflammable and less volatile than the common gasoline, especially for such engines as are installed in boats and aircraft. In using such fuels it is dimcult to attain gasiflcation sufficient to bring 15 about ignition from an ordinary spark plug. If suilicient heat is put into the mixture at the carbureter this heat is largely dissipated in travel through manifolds, etc., before it reaches the spark plug, and excessive condensation results 20;

during the compression stroke. By shielding the priming plug in a recess having a restricted communication with the compression chamber, as this so-called safety fuel is compressed by the piston, mechanical heat from friction or wire drawing is 26 put into a small percentage of the mixture as it ispushed by the compression of the piston into the recess containing the priming plug. The point of. ignition of this plug is in close proximity to the restricted passage and a large percentage of 30 the heat is available for gasifying a portion of the mixture in the zone of the spark "gap where it will be ignited before such heat has been dissipated to any large extent; therefore the principle of developing heat in a portion of the gas charge right 30" characteristics of the spark plugs; 5'0- Fig. 4 is a diagrammatic view of an ignition system using other spark plugs;

Fig. 5 is a vertical section through a two-cycle engine having a shielded priming plug; and

Fig. 6 is a diagrammatic view of the. ignition system of Fig. 5. v

The four-cycle engine shown in Fig. 1 is of any suitable construction, having a cylinder I with a water-jacketed wall 2, explosion driven mem- I her or piston 3, inlet valve 4 and exhaust valve 5. Spark plugs 6 and I are set in recesses 8 and 9, respectively, which are preferably formed at draining angles in the head of the cylinder to enable liquid fuel and oil to drain oil-into th cylinder. Y e

' Plug 6 is preferably any suitable type of "cold plug selected for its rapid heat dissipating properties. The particular plug 6 shown in Figs. 1 and 2 is a B. G. Hornet No. 4 having a small mica insulator l0, although this particular plug is shown simply for purposes of illustration as any other plug having good heat dissipating properties may be used equally well. 'Plug. t has its spark gap extending well into the combustion chamber of the cylinder head and is preferably pointed toward the center of the combustion space so that ignition from this plug will spread instantly throughout the entire compressed charge. I

Priming plug I is preferably selected for its good insulating properties, the particular plug 1 shown in Figs. 1 and 2 being a Robert Bosch midget 12 mm. plug having a so-called petticoat porcelain insulator l2 which is a good high tension insulator. Recess 9 containing plug 1 is preferably set at such an angle that its entrance is adjacent the water jacketed wall 2 of the cylinder, this being the region of the combustion chamber where the radiant heat is at a minimum.

Plugs 6 and I may be connected in series or in parallel and may be functioned by any suitable source of timed interrupted current such as a dual ignition magneto or a battery controlled by a suitable distributor or breaker. In the system of Fig. 2, wherein the two plugs are permanently connected in circuit with the energizing current, induction coil l3 has its primary winding connected to any suitable source of timed interrupted current and has a secondary winding l4 which is preferably grounded at its midpoint. Winding l4 has one end connected to plug 6 and the other end connected to plug 1. Grounding-of secondary winding M at its midpoint reduces the danger of failure of ignition since, if one plug fails due to any cause such as its terminal connector becoming detached, the other plug will continue to operate as before.

The operating characteristics of plugs 6 and I are illustrated graphically in Fig. 3 wherein the ordinates represent electrical ignition efliclency in terms of percentage and the abscissae represent temperature in degrees Fahrenheit. Under starting conditions and idling and low speeds, priming plug I functions at 100% of its electrical ignition efficiency, having sufllcient insulating surface to prevent fouling. When the temperature rises above about 250 F. the electrical ignition efficiency of plug 1 diminished due to the presence of a short-circuiting element of gas generated in the zone of the spark gap. Around 500 F. the electrical ignition efficiency of plug I drops sharply until at 750 F. it has only about 50% of its original potential in the center of hotness of its spark. An ordinary four-cycle engine of the type shown in Fig. 1 will develop a maximum temperature of around 2000 F. at which plug 1 may be completely short-circuited.

At the time the electrical ignition efliciency of plug 1 begins to fall the increasing temperature will have cleaned plug 6 of any surface condensation which has caused leakage and short-circuiting of the high tension current in this plug. As this deposit burns off, starting around 250 F., the electrical ignition efficiency of plug 6 rises sharply, and when the deposit is com letely burned off plug 6 will function as the mair. ignition point at 100% of its electrical ignition efficiency. The dotted line in Fig. 3 is a composite curve representing the combined ignition characteristics of plugs 6 and 1. Up to about 250 F. this curve is coincident with the curve of plug 1 which is operating at 100% of its efiiciency. At that point the efflciency of plug I drops slightly while that of plug 5 rises sharply, the combined efficiency of the plugs being about 180% at 500 F. as shown by the dotted curve. At 750 F. the combined efllciency of the plugs is about 150% and above that temperature the efficiency decreases rapidly, dropping to 100% when plug 1 is completely short circuited. When the combustion chamber cools due to continued idling or operating at lost speeds the action of the plugs is reversed but the combined efliciency of the plugs never drops below the maximum or 100% cmciency of either plug alone.

The ignition system of Fig. 4 is similar to that shown in Fig. 2 except that spark plugs I5 and I6 are two of the series made by the Champion Spark Plug Co., cold plug l5 being the Champion 10 R-1 and priming plug it being the Champion #7. Plug l5 has a small insulating surface l1 and metal gaskets I8, I 9, and 20 contacting with the metal shank whereby the radiant heat impinging on the plug is rapidly dissipated. Plug l6 has an elongated porcelain insulator 2| sufiicient to prevent fouling by deposited carbonaceous material. These plugs have the same general characteristics illustrated in Fig. 3.

The vertical two-cycle engine shown in Fig. 5

adjacent the air-cooled cylinder wall.

Plug 34 may be any suitable type of cold plug, that shown in Figs. 5 and 6 being a Champion R-2 having a small insulating surface 36 and metal gaskets 31 and 38 contacting with the metal shank. Plug may be any suitable type 35 of priming plug and in the form here shown is a Champion 14 m. m. special plug having an I elongated porcelain insulator 39 and an outer metal jacket or bushing 40 which surrounds the spark gap, forming a recess or pocket 4| having 40 a restricted orifice or passage 42. This passage is disposed at such an angle to recess 4| that the wall of the passage absorbs'the radiant heat of combustion which enters the passage and thereby prevents such heat from directly impinging on and overheating plug 35 which in some engines would become excessively hot if mounted in a more exposed position. Bushing 40 is made of heat absorbing materials such as iron or steel and hence the wall of passage 42 does not reflect heat especially since said wall is usually coated with carbon. Bushing 40 may be of any suitable diameter, for example it may have a 7 S. A. E. thread adaptable to various four-cycle automobile engines as well as to the two-cycle engine of Fig. 5. This bushing may be furnished as a part of the plug or may be formed integral with or secured to the cylinder head. An advantage of making the bushing a part of the cylinder head,

and using different sized plugs, is that it becomes 00 impossible to insert the plugs in the wrong positions. In the example given above plug 34 is 18 m. m. in diameter, which is considerably larger than plug 35.

On the compression stroke piston 26 forces a small amount of the fuel charge through passage 42 into recess 4!. Passage 42 is narrow enough to b 1 develop mechanical heat of friction in the charge passing through it and since the spark gap of plug 35 is in close proximity to passage 42 the 20 mechanical heat of friction will gasify a portion of the charge in the zone of the spark gap where the charge will be ignited before such heat has been dissipated to any large extent.

,Scavenging of recess 4|, is accomplished auto- 76 The engine is 25 the pressure in the cylinder and most of the exhaust gas flows out of said recess. On the following compression stroke the compressed fresh mixture forces the residual exhaust gas in recess I back to the base of the plug. The points of the spark gap are-close enough to passage l2,

and theclearance back of the points is sufficient,

to allow such residual exhaust gas to be pushed back away from the points on each compression stroke.

Although no one spark plug has yet been designed to combine the advantages of good electrical insulation and good heat dissipation, these advantages are eifectively combined in the two or more plugs described above. I do not limit myself to two spark plugs in a cylinder, as I may employ a plurality of cold plugs and a plurality of priming plugs in one cylinder, or in some cases may use a single plug of one type and a plurality of plugs of another type in one cylinder connected either in series or in parallel and operated in any suitable manner. Many variations in the arrangement and mode of operation of the spark plugs and the ignition system as a whole will readily occur to those skilled in the art without departing from the scope and spirit of the appended claims.

The invention claimed is:

l. Method'of maintaining uniform combustion of a compressed mixture in the combustion space of a combustion engine which comprises subjecting successive charges of said mixture to a plurality of timed interrupted sparks which vary oppositely in intensity with variations in temperature within said combustion space.

2. Method of maintaining uniform combustion of a compressed mixture in the combustion space of a combustion engine which comprises subject,

ing successive charges of said mixture to a pmrality of timed interruptedsparks varying oppo-.

sitely in intensity with variations in temperature 7 within said combustion space and having at all times a combined intensity at least equal to the maximum intensity of either of said sparks alone.

3. Method of maintaining uniform combustion of a compressed mixture in the combustion space of a combustion engine which comprises subjecting successive charges of said mixture to a timed interrupted spark having a maximum intensity at relatively low temperatures within said combustion space and simultaneously subjecting each charge of said mixture to a timed interrupted spark having a maximum intensity at relatively high temperatures within said combustion space.

4. An ignition system for combustion engines comprisin a spa k plug having high electrical ignition efllciency when subjected to relatively low temperatures and low electrical ignition efhciehcy when subjected to relatively high temperatures within the combustion space, and a second spark plug in circuit therewith having high electrical ignition emciency when subjected to relatively high temperatures and low electrical ignition emciency when subjected to relatively low temperatures within the combustion space.

5. An ignition system for-combustion engines comprising a'spark plug having maximum electrical ignition eiiiciencywhen subjected to relatively low temperatures within the combustion space, and a second spark plug in circuit with said first plug having-maximum electrical ignia,oss,aos

tion emciency when subjected to relatively high temperatures within said combustion space.

6. An ignition system for combustion engines comprising a spark plug having high insulating ,properties and maximum electrical ignition emciency when subjected to relatively low temperatures within "the combustion space, a second spark plug having rapid heat dissipatingproperties and maximum electrical ignition eiilciency when subjected to relatively high temperatures within said 10 combustion space, and means for simultaneously energizing said spark plugs.

'7..An ignition system for combustion engines comprising a spark plug having high insulating properties and maximum electrical ignition efll- 15 either spark plug alone.

8'. An ignition system for combustion engines 7 comprising a pair of spark plugs having individual electrical ignition characteristics which vary over the range of temperatures developed in the combustion space of the engine at varying engine speeds, one of said spark plugs having a maximum the maximum electrical ignition efliciency of 25 electrical ignition eiiiciency in the lower portion of said temperature range, the other of said spark plugs having a maximum electrical ignition emciency in the upper portion of said temperature range, and said spark plugs together having a combined electrical ignition characteristic over the entire temperature range at least equal to the maximum electrical ignition emciency of either 0 spark plug, alone.

9. An ignition system for combustion engines comprising a pair of spark plugs having individual [electrical ignition characteristics which vary over the range of temperatures developed in the combustion space of the engine at varying engine speeds, one of said spark plugs having an electrical ignition emciency attaining a maximum in the lower portion 01' said temperature range and dropping sharply in the upper portion of said temperature range, and the other of said spark plugs having low electrical ignition efliciency in the lower portion of said temperature range and high electrical ignition eihciency in the upper portion of said temperature range, and means for simultaneously energizing said spark plugs.

10. An ignition system for combustion engines comprising a pair of spark plugs having individual electrical ignition characteristics which vary over the range of temperatures developed in the combustion space of the engine at varying engine speeds, one of said spark plugs having an electricalignition efficiency attaining a maximum in. the lower portion of said temperature range and dropping sharply in the upper portion of said temperature range, and the other 01' said spark plugs having an electrical ignition efllciency at a minimum in the lower portion of said temperature range and increasing sharply at the point where the electrical ignition efficiency of the first mencomprising. a spark plug having suiiicient insulation adjacent its spark gap to prevent fouling at the relatively low temperatures developed in the combustion space of the engine when the engine is started and operated at low speeds, a second spark plug having rapid heat dissipating properties and high electrical ignition eficiency at the relatively high temperatures developed in said combustion space when the engine is operated at high speeds, and means for simultaneously energizing said spark plugs.

12. A combustion engine comprising a combustion space having a recess for a spark plug, a-

spark plug having relatively high insulating properties and relatively low heat dissipating properties mounted in said recess, a restricted passage permanently connecting said recess with said combustion space to minimize radiation of heat to said spark plug, and a second spark plug adapted for rapid heat dissipation having its spark gap extending into said combustion space.

13. A combustion engine comprising a com-, bustion space, a spark plug having a high tension insulator in constant communication with said combustion space, means for shielding said spark plug from the radiant heat of combustion, and a second spark plug having a rapid heat dissipating insulator and a spark gap mounted in exposed position in said combustion space.

14. A combustion engine comprising a combustion space and a plurality of spark plugs connected with said combustion space and adapted to spark simultaneously, one of said spark plugs having a high tension insulator and a spark gap shielded from the radiant heat in said combustion space, and another of said spark plugs having a rapid heat dissipating insulator and a spark gap mounted in exposed position in said combustion space.

15. A combustion engine comprising a combustion space having an outer cooling surface and a plurality of spark plugs set at draining angles communicating with said combustion space and adapted to spark simultaneously, one of said spark plugs having relatively high insulating properties and relatively low heat dissipating properties and having a spark gap shielded from said combustion space adjacent said cooling surface, and another of said spark plugs having relatively high heat dissipating properties and relatively low insulating properties and having a spark gap mounted in exposed position in said combustion space.

16. An ignition system for combustion engines comprising a spark plug having relatively high insulating properties and relatively low heat dissipating properties and a second spark plug in circuit therewith having rapid heat dissipating properties and relatively low insulating properties, and means for energizing said spark plugs.

17. An ignition system torcombustion engines comprising a spark plug having relatively high insulating properties and relatively low heat dissipating properties and a second spark plug hava primary winding connected to said source of current and a secondary winding connected to said spark plugs.

19. A combustion engine comprising a combustion space, a spark plug having relatively -high insulating properties and relatively low heat dissipating properties communicating with said combustion space, means for heating a portion of the compressed charge adjacent said spark plug, and

a second spark plug adapted for rapid heat dissipation having its spark gap extending intosaid combustion space. 4

20. A combustion engine comprising a combustion space containing a recess, a spark plug having relatively high insulating properties and relatively low heat dissipating properties mounted in said recess, a passage connecting said recess with said combustion space, said passage being narrow enough to develop mechanical heat of friction in the compressed charge passing through said passage into said recess, and a second spark plug adapted for rapid heat dissipation having its spark gap extending into said combustion space.

21. A combustion engine comprising a combustion space containing a recess for a spark plug, a passage connecting said recess with said combustion space, a spark plug having relatively high insulating properties and relatively low heat dissipating properties mounted in said recess and having a spark gap adjacent said passage, said passage being narrow enough to develop mechanical heat of friction in the compressed charge passing through said passage into said recess whereby to gasify the charge adjacent said spark gap, and a second spark plug adapted for rapid heat dissipation having its spark gap extending into said combustion space.

22. A cylinder head for a combustion engine containing a recess for the reception of a spark plug having high tension insulating properties and a recess of different size for the reception of a spark plug having rapid heat dissipating properties.

23. A cylinder head for a combustion engine containing a plurality of recesses of different sizes for the reception of spark plugs of diflerent sizes, one of said recesses extending directly into the combustion side of said cylinder head and another of said recesses being shielded from the combustion side oi'said cylinder head and having a restricted passage connected thereto.

WILLIAM HARPER, JR. 

